Feasibility varies between localities depending upon the coverage of the water distribution system and any technical constraints it imposes. For a strategic health authority with an average population of 5 million we estimate the capital costs of the water plant would be in the range of £15 million to £25 million and the recurrent costs of the operation of the plant and the fluoride chemicals around 80 pence per head of population per year. This compares to some £40 per person currently spent each year on national health service primary care dental services.